Weird stone like fungus

[ClimbingTN]

This seems almost petrified. The single one on the broken piece is rock hard. The two next to each other are very hard too.

 

[Serf Life]

Looks like a terrestrial limpet

 

[ClimbingTN]

Looks like a terrestrial limpet

Huh? Pulling my leg? I couldn’t find anything.

 

[Serf Life]

No idea what it is, just looks like a limpet. @KTSmith may have an idea

 

[KTSmith]

This is where 2 minutes with a razor blade and a magnifying glass would save a lot of guessing.
I think I see a pore surface and the hard consistency points towards Phellinus, and the dimensions suggest P. robustus. Could be! Again, not much to go on.